It's one which might start out a bit slow and twee in Hobbiton where Tolkien's earlier fellowship - one hobbit, 13 dwarfs, a wizard with a plan - meet for the first time.

But having got the introductions out of the way, and having convinced the homely hobbit to help the homeless dwarves on their quest, The Hobbit: An Unexpected Journey is soon snowballing its way thrillingly, often hilariously, to end at a point which is only six chapters into what was only a 19-chapter book.

That it takes nearly three hours to get only that far might seem excessive. That it pulls in Tolkien material from beyond The Hobbit might seem like it's taken the children's tale and forced it to grow up - and fill what will be, by this trilogy's end, eight hours-plus of screentime.

But as lengthy as this first instalment is, it's a cracking start.

It's also a film which feels looser, funnier and often outright scarier than Jackson's last venture into this territory.

Fortunately, its last hour just flies by. There, having already survived trolls, stone giants and elven vegetarian cooking, the merry little gang find themselves bouncing between masses of goblins, a gang of orcs, a pack of wargs and, of course, a Gollum.

The effect of all that is more electrifying than exhausting. While it's arguable that it's a better film than the previous Tolkien epic starter, The Fellowship of the Ring, it's surely a better theme park ride.

But this madly involving Middle-earth rollercoaster isn't just a product of state-of-the-art special effects hocus-pocus. Thankfully, it's still grounded in character and that old-fashioned screen software called "acting" - Martin Freeman's Bilbo is clearly the best screen embodiment of a hobbit yet.

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If Andy Serkis' motion-captured Gollum stole the show in the previous trilogy, he gets another chance in the pivotal face-off between him and Bilbo as they riddle for that damn ring.

Elsewhere, McKellen is a slightly more vulnerable Gandalf than the wise sage of his later years, while Richard Armitage as dwarf leader Thorin Oakenshield sure gives good hero-glower as the pint-size warrior out to recapture his birthright from the dragon Smaug - largely unseen here - who now sits Scrooge McDuck-like on the dwarves' old treasury.

Even Manu Bennett as chief orc Azog shines from beneath whatever it is that has rendered him so brutally ugly.

He's got some cracker (subtitled) lines too: "Send word to the master. We have found the dwarf scum." Which gets my vote for being the "These are not the droids you are looking for" of this franchise.

But of course, this is not just Jackson and his co-boffins returning to Middle-earth for the prequel, made inevitable by the success of their Lord of the Rings trilogy. It's also a film pioneering high definition 48 frames per second 3D (though it's mostly in cinemas in conventional 3D and 2D), which has already had its detractors.

I've suffered through some headache-inducing 3D in past years. But here, other than being initially disconcerted by the clarity and feeling my optic nerves recalibrating to the immersive effect - the dwarves' invasion of Bilbo's house has the weird intimacy of a stage play - I suffered no ill effects. Other than being completely dazzled, in a good way.

No, the only technical quibble, which was likely specific to the media screening I attended at Park Road Post, was with the sound mix. The start of the film suffered from some wobbly frequencies, while during the pivotal riddle scene between Bilbo and Gollum, some of the dialogue sounded muddied.

And while on the subject of what's coming out of the speakers, The Hobbit does suffer from a relentless, dreary soundtrack. Howard Shore's orchestral score echoes his music from the earlier trilogy but still detracts from the atmosphere in the quieter moments.

Oh well, at least the dwarves limit themselves to two singalongs. Lovely voices they have too. But their real strength is comedy in a movie that's possibly got more laughs in it than the entire LOTR trilogy.

It's not just the little folk delivering some memorable gags - a trolls' campfire scene almost becomes its own Middle-earth chef show; scenes featuring Sylvester McCoy's woodland wizard Radagast and a dying hedgehog are truly nutty; so too is Barry Humphries as the Great Goblin, a grotesque creature who manages to be uglier than Jabba the Hutt by virtue of having what appears to be a giant testicle for a chin.

Yes, the monsters are better than they were this time last decade. And there's just enough to connect it to the previous trilogy - especially the reappearance of Middle-earth senior staff played by Hugo Weaving, Cate Blanchett and Christopher Lee - without feeling we've been down this way before.

The first thing you see at the start of An Unexpected Journey, is the lighting of a candle as an older Bilbo recalls his adventurous days in flash-forward to the LOTR era. Maybe the implied question is: can The Hobbit hold a candle to what's gone before?